The subject invention is directed toward the fastener art and, more particularly, to a fastener of the type generally referred to as a "push-in" or "drive" fastener.
"Push-in" or "drive" fasteners of a variety of types and styles are well known in the art. Typically, as shown in U.S. Pat. Nos. 4,396,329 and 4,728,238 they are arranged to be driven axially into preformed openings in a work piece and to engage therein by virtue of laterally extending flexible tabs or wing-like members.
An ongoing problem with such fasteners has been the relationship between the installation or insertion forces and the removal forces. Ideally, it would be desirable in many situations to have a design wherein the insertion forces are extremely low and the removal forces extremely high. With the prior art designs, however, these forces were generally nearly equal. Attempts to reduce the forces resisting installation while increasing the forces resisting removal have typically involved changing the shape of the tabs, their angle of inclination, or their manner of connection to the fastener shank. These changes have generally been of marginal value.